At a meeting with NATS chief executive Richard Everitt on 16 January, Scottish Secretary of State Helen Liddell is expected to express anxiety over delays to the £60million control facility at Prestwick.

NATS postponed the Prestwick centre as part of a £200million cost-cutting package to relieve the dire financial pressure facing NATS and the UK air traffic system.

Prestwick – one element of a wider £1.2 billion plan of investment agreed on privatisation – is part of a two-centre strategy with Swanwick to guarantee capacity and UK air safety in the event, for example, of a terrorist attack disabling one of the centres.

Iain Findlay, aviation officer for the air traffic controllers’ union Prospect, said: "Just a few months ago, everyone recognised the necessity for urgent and continuous investment in air traffic control infrastructure. Indeed, the Labour government promoted privatisation of NATS as the route to secure investment.

"We argued that the proposed financing structure would leave NATS saddled with huge debt, reliant on bank lending and restrained from increasing income."

Prospect is calling on the economic regulator to change the existing draconian pricing regime saying the events of 11 September exacerbated an already fragile situation which was present at the time of privatisation.

As well as trying to postpone investment, NATS’ are accelerating support staff job cuts and engineering reductions.

The union is calling on the government to intervene to ensure long-term investment. Says Findlay: "The government should consider a rebate of around £300 million on the original distorted NATS sale price of £700 plus million to reduce the debt. This was regarded as the best air traffic service in the world. We don’t want a Railtrack of the skies."